A defect of a repetitive pattern (a line-and-space pattern such as an interconnection pattern) formed in a surface of a semiconductor wafer or a liquid crystal display substrate (collectively referred to as “substrate”) is inspected in a process of producing a semiconductor circuit element or a liquid crystal display element. In automatic surface inspecting apparatuses, the substrate is placed on a tiltable stage, the surface of the substrate is irradiated with testing illumination light (non-polarized light), an image of the substrate is captured based on diffracted light (for example, first-order diffracted light) generated from the repetitive pattern on the substrate, and a defective point of the repetitive pattern is identified based on a contrast of the image. Additionally, in conventional surface inspecting apparatuses, a defect of a repetitive pattern having a different repetitive pitch on the substrate can be inspected by adjusting the tilt of the stage.
Patent Document 1: Japanese Patent Publication Laid-Open No. 10-232122
However, in conventional surface inspecting apparatuses, when the repetitive pitch of the repetitive pattern is smaller than a given value (=(order of diffraction)×(wavelength of illumination light)/2), diffracted lights are not generated in principle from the repetitive pattern, and defects cannot be inspected. In the case where the repetitive pitch is brought close to the given value, due to restriction of a mechanical layout of an illumination system or a light acceptance system in the apparatuses, defect inspection can hardly be realized by diffracted lights.
In order to meet the finer repetitive pitch (that is, the finer line and space of the interconnection pattern or the like), it is thought that a wavelength of the illumination light is shortened to decrease the given value. However, a type of a light source is limited, and the light source becomes large and expensive. Furthermore, disadvantageously materials of optical elements constituting the illumination system or light acceptance system are limited to expensive ones.
An object of the present invention is to provide a surface inspecting apparatus which can surely meet a finer repetitive pitch without shortening the wavelength of the illumination light.